Pollen-Mediated Dispersal of Glyphosate-Resistance in Palmer Amaranth under Field Conditions

Abstract

In addition to being a strong competitor with cotton and other row crops, Palmer amaranth has developed resistance to numerous important agricultural herbicides, including glyphosate. The objective of this study was to determine if the glyphosate-resistance trait can be transferred via pollen movement from a glyphosate-resistant Palmer amaranth source to a glyphosate-susceptible sink. In 2006 and 2007 glyphosate-resistant Palmer amaranth plants were transplanted in the center of a 30-ha cotton field. Susceptible Palmer amaranth plants were transplanted into plots located at distances up to 300 m from the edge of the resistant pollen source in each of the four cardinal and ordinal directions. Except for the study plots, the interior of the field and surrounding acreage were kept free of Palmer amaranth by chemical and physical means. Seed was harvested from 249 and 292 mature females in October 2006 and 2007, respectively. Offspring, 14,037 in 2006 and 13,685 in 2007, from glyphosate-susceptible mother plants were treated with glyphosate when the plants were 5 to 7 cm tall. The proportion of glyphosate-resistant progeny decreased with increased distance from the pollen source; approximately 50 to 60% of the offspring at the 1- and 5-m distances were resistant to glyphosate, whereas 20 to 40% of the offspring were resistant at the furthest distances. The development of resistance was not affected by direction; winds were variable with respect to both speed and direction during the peak pollination hours throughout the growing season. Results from this study indicate that the glyphosate-resistance trait can be transferred via pollen movement in Palmer amaranth.

Pollen‐mediated transfer of herbicide resistance in Echinochloa crus‐galli

“…In other words, under typical field conditions, gene flow at shorter distances appears to be limited by factors other than pollen load. The longevity of barnyardgrass pollen is unknown, but it is possible that extended pollen viability would offset a reduction in pollen dispersal, as suggested by Liu et al A lack of association between frequency of wind flow and gene flow levels has also been demonstrated in other studies …”

“…Gene flow is a natural phenomenon among arable weed communities, but it was not considered to be a management issue until the evolution of herbicide resistance in weed populations. Herbicide resistance will most likely be expressed in pollen if resistance is nuclear encoded, and may subsequently spread to susceptible weed populations within the vicinity through PMGF . For anemophilous grass species, pollen movement has been shown to be an important avenue for resistance spread .…”

Rethinking Outreach: Collaboration Is Key for Herbicide-Resistance Management

“…Infestations from outside the field are a major concern (Bagavathiannan et al, 2013a). Seed are readily moved by water and equipment into clean fields, and viable pollen may move up to 0.25 mile and confer resistance to new areas (Sosnoskie et al, 2012). Turnrows, ditchbanks and adjacent fields can be major sources of seed to move into otherwise clean fields.…”

An analysis of polygenic herbicide resistance evolution and its management based on a population genetics approach

“…Wats. ), a major cross-pollinating weed, could spread pollen up to 300 m (Sosnoskie et al, 2012). Therefore pollen flush from susceptible weeds would alter the overall frequency of herbicide resistance alleles in a weed population and thereby reduce the herbicide resistance level of weed populations.…”